1. Field of the Invention
The present invention relates to a cylinder-injection fuel injection valve mounted in a fuel injection valve insertion port on a cylinder head for injecting fuel through a fuel injection aperture into a cylinder.
2. Description of the Related Art
FIG. 5 is a cross-section showing the complete construction of a conventional cylinder-injection fuel injection valve 1 (hereinafter simply xe2x80x9cfuel injection valvexe2x80x9d), FIG. 6 is a partial enlargement of FIG. 5, and FIG. 7 is a plan view of the fork in FIG. 5.
The fuel injection valve 1 comprises: a housing main body 2; a valve assembly 3 disposed within the housing main body 2; a solenoid assembly 4 disposed within the housing main body 2; and an elastic seal ring 7 with a wave-shaped cross-section in the axial direction disposed between a fuel injection valve insertion port 6 in a cylinder head 5 and the tip of the housing main body 2.
The valve assembly 3 comprises: a stepped, hollow, cylindrical valve main body 11 having a small-diameter cylinder portion 9 and a large-diameter cylinder portion 10; a valve seat 13 having a fuel injection aperture 12 secured within an end portion of the valve main body 11; a needle valve 14 being a valve body moved into and out of contact with the valve seat 13 to close and open the fuel injection aperture 12; a swirler 15 for guiding the needle valve 14 in the axial direction as well as imparting a swirling motion to the fuel as the fuel flows towards the fuel injection aperture 12; and a movable armature 16 secured to the other end of the needle valve 14.
An intermediate portion of the needle valve 14 is formed with: a guide portion 17 for guiding the needle valve 14 as it slides along the inner circumferential surface of the valve main body 11; and a flange portion 19 for contacting a spacer 18 within the housing main body 2.
The housing main body 2 comprises: a first housing 21 having a flange for mounting the fuel injection valve 1 on the cylinder head 5; a second housing 22 connected to one end of the first housing 21; and a holder 23 connected to the other end of the first housing 21.
The solenoid assembly 4 comprises: a coil 24 of wound wire; a bobbin on which the coil is mounted; a cylindrical core 26 attached to an inner circumferential portion of the bobbin 25; a sleeve 27 secured to the inside of the core 26; a spring 28 compressed and disposed between an end portion of the sleeve 27 and an end portion of the needle valve 14 for pressing the needle valve 14 against the valve seat 13; and terminals 29 electrically connected to the wire of the coil 24.
The swirler 15 constituting part of the valve assembly 3 is a hollow, cylindrical member which has a central aperture 30 at its center for supporting the needle valve 14 so that the needle valve 14 can slide in both axial directions, and is provided with: a first end surface 31 in contact with the valve seat 13; a second end surface 32 at the opposite end from the valve seat 13; and an outer surface 34 between these two end surfaces 31, 32 which comes into contact with an inner circumferential surface 33 of the valve main body 11.
First passages 35 extending radially are formed in the second end surface 32 of the swirler 15 such that fuel flows through the first passages 35 from inner circumferential portions of the second end surface 32 to outer circumferential portions thereof.
Second passages 36 extending longitudinally and connected to the first passages 35 are formed in the outer surface 34 of the swirler 15.
Swirling grooves 37 are formed in the first end surface 31 of the swirler 15 in connection with the second passages 36 for generating a swirling current.
The tip of a fuel injection valve 1 of the above construction is inserted into the fuel injection valve insertion port 6 in a cylinder head 5. An insertion port shoulder portion 38 and a countersunk face 39 are formed within the fuel injection valve insertion port 6.
A metal gasket 40 is disposed between the flange 20 and the countersunk face 39.
As shown in FIG. 7, both sides of the flange 20 are pressed against the cylinder head 5 by a fork 41 secured to the cylinder head 5 by a securing bolt 42, whereby the gasket 40 is pressed against the countersunk face 39 and the seal ring 7 is compressed. As a result, one side 43 of the seal ring 7 presses against a contact surface 44 of the holder 23 and the other side 45 presses against the surface of the insertion port shoulder portion 38, preventing the high-temperature, high-pressure combustion gas in the cylinder from leaking into the housing main body 2 by means of a so-called xe2x80x9cdouble seal constructionxe2x80x9d.
Next, the operation of a fuel injection valve 1 of the above construction will be explained.
When an electric current is supplied to the coil 24 of the solenoid assembly 4 from outside through the terminals 29, a magnetic flux is generated in the magnetic passage formed by the movable armature 16, the core 26, and the housing main body 2, whereby the movable armature 16 is attracted against the elasticity of the spring 28 towards the core 26. Thus, the needle valve 14, which is integrated with the movable armature 16, is moved upwards as far as the position where the flange portion 19 of the needle valve 14 contacts the spacer 18. The guide portion 17 is guided in the axial direction by the inner circumferential surface of the valve main body 11 as the needle valve 14 moves upwards.
As the needle valve 14 moves upwards, the tip of the needle valve 14 is separated from the valve seat 13, forming a gap between the tip thereof and the valve seat 13. As a result, high-pressure fuel fed from a fuel supply pipe 46 flows in through a fuel filter 8, through a fuel passage 47 within the sleeve 27, through the gap formed between the needle valve 14 and the valve main body 11, through the first passages 35 in the second end surface 32 into the second passages 36 in the outer surface 34, then the high-pressure fuel flows into the swirling grooves 37 of the first end surface 31. The fuel forms a swirling current inside the swirling grooves 37 and is sprayed from the fuel injection aperture 12 into the cylinder (not shown).
In a fuel injection valve 1 of the above construction, the valve main body 11 is secured by a crimped portion 50 formed on the tip of the first housing 21, but a problem is that, since the crimped portion 50 does not have a smooth, flat surface, it is not possible to prevent high-temperature, high-pressure combustion gas from leaking to the housing main body 2 even if one side 43 of the seal ring 7 is in contact therewith, requiring that a holder 23 having a smooth, flat contact surface 44 be purposely prepared and pressed fitted over the tip of the first housing 21.
The present invention aims to solve the above problem and an object of the present invention is to provide a cylinder-injection fuel injection valve enabling manufacturing costs to be reduced by eliminating the need for the holder conventionally required as a contact surface for the seal ring, as well as facilitating the assembly process by eliminating the need to press fit the holder.
To this end, according to the present invention, there is provided a cylinder-injection fuel injection valve comprising: a housing main body; a valve assembly disposed within the housing main body and provided with: a valve main body having a large-diameter cylinder portion and a small-diameter cylinder portion; a valve seat having a fuel injection aperture secured within the tip of the valve main body; and a valve body moved into and out of contact with the valve seat to close and open said fuel injection aperture; a seal held between a cylinder head and a shoulder portion between the large-diameter cylinder portion and the small-diameter cylinder portion when the tip of the valve assembly is inserted into an insertion port in a cylinder for preventing combustion gas in a cylinder from leaking to the housing main body; and a securing means for securing the valve main body to the housing main body disposed between the side of the large-diameter cylinder portion and an engaging portion formed on the tip of the housing main body.